The Internet of things (IoT) is the inter-networking of physical devices, vehicles, buildings, and other items embedded with electronics, software, sensors, actuators, and network connectivity that enable these objects to collect and exchange data. IoT is expected to offer advanced connectivity of devices, systems, and services that goes beyond machine-to-machine (M2M) communications and covers a variety of protocols, domains, and applications.
IoT can be encapsulated in a wide variety of devices, such as heart monitoring implants; biochip transponders on farm animals; automobiles with built-in sensors; automation of lighting, heating, ventilation, air conditioning (HVAC) systems; and appliances such as washer/dryers, robotic vacuums, air purifiers, ovens or refrigerators/freezers that use Wi-Fi for remote monitoring. Typically, IoT devices encapsulate wireless sensors or a network of such sensors.
Most IoT devices are wireless devices that collect data and transmit such data to a central controller. There are a few requirements to be met to allow widespread deployment of IoT devices. Such requirements include reliable communication links, low energy consumption, and low maintenance costs.
To this aim, an IoT device and connected wireless sensors are designed to support low power communication protocols, such as Bluetooth low energy (BLE), LoRa, and the like. However, IoT devices utilizing such protocols require a battery, for example, a coin battery. The reliance on a power source such as a battery, is a limiting factor for electronic devices, due to, for example, cost, size, lack of durability to environmental effects, and frequent replacement. As an alternative to using batteries, power may be harvested from sources such as light, movement, and electromagnetic power such as existing radio frequency transmissions. In order to minimize the power consumption, IoT devices are designed with the minimum required components or implementing low-power consumption oscillators.
Conventional RF circuitry (such as amplifiers and oscillators) may use a central-tap on the inductor/transformer to bias the circuit devices (for example, to provide a supply). Some oscillator devices are typically referred to conventional internal local oscillators and power oscillators interface with the antenna (i.e., there is no active amplifying or buffering stage between the oscillator and the transmission antenna). When used in an antenna, the central tap connection adds an on-substrate trace that may impact antenna radiation, and may limit the antenna type, since it requires a point on the antenna that has a DC-short to the oscillator AC ports. In low cost substrate solutions such as a Polyethylene terephthalate (PET) and paper, single-layer materials may be used to reduce cost, or only a single layer used for routing.
This may further limit a center-tap connection. Eliminating the central tap may impose a challenge on the oscillator bias. This is in addition to the challenge of biasing the oscillator which has a very low supply voltage. Lowering the supply of the oscillator to <200 mV range enables sufficiently low power consumption but comes with bias voltages that are outside the 0V-200 mV range, given the topology that avoids the central tap.
It would therefore be advantageous to provide a solution to design a transmitter without using very low power requirements that would overcome the challenges noted above.